Dilution of proparacaine in balanced salt solution reduces pain of anesthetic instillation in the eye.

BACKGROUND AND OBJECTIVES: Proparacaine (P), 0.5%, is often applied topically to the eye to diminish the pain of injection of anesthetic for eye surgery; however, application of 0.5% P itself can cause some degree of discomfort. This study evaluated the use of balanced salt solution to dilute P before instillation in the eye to prevent discomfort. METHODS: In a double-blinded manner, 42 consenting adults about to undergo cataract surgery were given 0.5% P in one eye and 0.03% P in the other eye. One minute later the same solutions were instilled into each eye. Ten minutes later, 0.5% P was instilled into both eyes. After each instillation the patients were asked to describe the pain in each eye on a 0 to 10 scale. RESULTS: Those receiving 0.5% as the first drop had a mean pain score of 1.28, which was greater than the score of 0.09 for the 0.03% P group (P < .01). No one reported pain after the second drop was applied 1 minute later. After receiving 0.5% P 10 minutes later, the group that had received 0.5% P reported a mean pain score of 0.09 while those who had received 0.03% P reported a score of 0.76, which was significantly greater than that reported by the 0.5% P group after the 10 minute instillation (P < .01) but significantly lower than the score reported after the first instillation of 0.5% P (P < .05). CONCLUSIONS: Dilution of P in balanced salt solution to a concentration of 0.03% produces a solution that is significantly less painful than 0.5% P and reduces the discomfort of the instillation of 0.5% P.

Modification of human serum albumin with N-(2,5-dinitro-4-fluorophenyl)-4-amino-2,2,6,6-tetramethyl-piperidinooxy radical.

Human serum albumin has been treated with the spin-labeling reagent indicated in the title. Ultraviolet spectral studies of the protein so modified suggest that reaction takes place at lysine and tyrosine sidechains; kinetic experiments indicate that there are two especially reactive amino groups of the protein which are preferentially modified. Evidence is presented that these groups include the one acetylated by aspirin (Lys-199) or those arylated by 2.6-dinitro-4-trifluoromethylbenzenesulfonate. Esr experiments show that bound spin labels have about the same correlation time expected for overall tumbling of the protein; ESR observations indicate that molecular freedom near the spin labels is not increased when the protein is transferred to 8 M urea.